diff --git a/contrib/src/sceneeditor/seSelection.py b/contrib/src/sceneeditor/seSelection.py
index b7d9b260dc..6dfa718f85 100644
--- a/contrib/src/sceneeditor/seSelection.py
+++ b/contrib/src/sceneeditor/seSelection.py
@@ -548,7 +548,7 @@ class SelectionRay(SelectionQueue):
         if xy:
             mx = xy[0]
             my = xy[1]
-        elif direct:
+        elif base.direct:
             mx = SEditor.dr.mouseX
             my = SEditor.dr.mouseY
         else:
diff --git a/direct/src/directnotify/RotatingLog.py b/direct/src/directnotify/RotatingLog.py
index 5eb5706c95..d7b9b06d34 100755
--- a/direct/src/directnotify/RotatingLog.py
+++ b/direct/src/directnotify/RotatingLog.py
@@ -4,7 +4,7 @@ import time
 
 class RotatingLog:
     """
-    A file() (or open()) replacement that will automatically open and write
+    An `open()` replacement that will automatically open and write
     to a new file if the prior file is too large or after a time interval.
     """
 
diff --git a/direct/src/directtools/DirectSession.py b/direct/src/directtools/DirectSession.py
index d004779d29..087348dfad 100644
--- a/direct/src/directtools/DirectSession.py
+++ b/direct/src/directtools/DirectSession.py
@@ -669,6 +669,8 @@ class DirectSession(DirectObject):
         if not taskMgr.hasTaskNamed('resizeObjectHandles'):
             dnp = self.selected.last
             if dnp:
+                direct = base.direct
+
                 if self.manipulationControl.fMultiView:
                     for i in range(3):
                         sf = 30.0 * direct.drList[i].orthoFactor
diff --git a/direct/src/directutil/DistributedLargeBlobSender.py b/direct/src/directutil/DistributedLargeBlobSender.py
index 39748a13a2..35b46761a7 100755
--- a/direct/src/directutil/DistributedLargeBlobSender.py
+++ b/direct/src/directutil/DistributedLargeBlobSender.py
@@ -56,7 +56,7 @@ class DistributedLargeBlobSender(DistributedObject.DistributedObject):
         except OSError:
             DistributedLargeBlobSender.notify.error(
                 'could not access %s' % bPath)
-        f = file(filename, 'rb')
+        f = open(filename, 'rb')
         self.blob = f.read()
         f.close()
         os.unlink(filename)
diff --git a/direct/src/directutil/DistributedLargeBlobSenderAI.py b/direct/src/directutil/DistributedLargeBlobSenderAI.py
index 648599731d..514033face 100755
--- a/direct/src/directutil/DistributedLargeBlobSenderAI.py
+++ b/direct/src/directutil/DistributedLargeBlobSenderAI.py
@@ -42,7 +42,7 @@ class DistributedLargeBlobSenderAI(DistributedObjectAI.DistributedObjectAI):
                     break
             # NOTE: there's a small chance of a race condition here, if
             # the file is created by another AI just after the stat fails
-            f = file(filename, 'wb')
+            f = open(filename, 'wb')
             f.write(s)
             f.close()
             os.chdir(origDir)
diff --git a/direct/src/dist/FreezeTool.py b/direct/src/dist/FreezeTool.py
index 9da47058e8..95d94c2ced 100644
--- a/direct/src/dist/FreezeTool.py
+++ b/direct/src/dist/FreezeTool.py
@@ -77,6 +77,8 @@ defaultHiddenImports = {
         'numpy.core._dtype_ctypes',
         'numpy.core._methods',
     ],
+    'pandas.compat': ['lzma', 'cmath'],
+    'pandas._libs.tslibs.conversion': ['pandas._libs.tslibs.base'],
 }
 
 # These are overrides for specific modules.
diff --git a/direct/src/dist/commands.py b/direct/src/dist/commands.py
index c14309ac03..191a5c019a 100644
--- a/direct/src/dist/commands.py
+++ b/direct/src/dist/commands.py
@@ -4,7 +4,6 @@ See the :ref:`distribution` section of the programming manual for information
 on how to use these commands.
 """
 
-import collections
 import os
 import plistlib
 import pkg_resources
@@ -211,8 +210,10 @@ class build_apps(setuptools.Command):
             # manylinux1/linux
             'libdl.so.*', 'libstdc++.so.*', 'libm.so.*', 'libgcc_s.so.*',
             'libpthread.so.*', 'libc.so.*', 'ld-linux-x86-64.so.*',
-            'libgl.so.*', 'libx11.so.*', 'libreadline.so.*', 'libncursesw.so.*',
-            'libbz2.so.*', 'libz.so.*', 'liblzma.so.*', 'librt.so.*', 'libutil.so.*',
+            'libgl.so.*', 'libx11.so.*', 'libncursesw.so.*', 'libz.so.*',
+            'librt.so.*', 'libutil.so.*', 'libnsl.so.1', 'libXext.so.6',
+            'libXrender.so.1', 'libICE.so.6', 'libSM.so.6',
+            'libgobject-2.0.so.0', 'libgthread-2.0.so.0', 'libglib-2.0.so.0',
 
             # macOS
             '/usr/lib/libc++.1.dylib',
diff --git a/direct/src/distributed/DistributedCameraOV.py b/direct/src/distributed/DistributedCameraOV.py
index a539b12794..bdf9369b45 100755
--- a/direct/src/distributed/DistributedCameraOV.py
+++ b/direct/src/distributed/DistributedCameraOV.py
@@ -24,7 +24,7 @@ class DistributedCameraOV(DistributedObjectOV):
         self.fixtures = fixtures
 
     def storeToFile(self, name):
-        f = file('cameras-%s.txt' % name, 'w')
+        f = open('cameras-%s.txt' % name, 'w')
         f.writelines(self.getObject().pack())
         f.close()
 
@@ -35,7 +35,7 @@ class DistributedCameraOV(DistributedObjectOV):
 
     def loadFromFile(self, name):
         self.b_setFixtures([])
-        f = file('cameras-%s.txt' % name, 'r');
+        f = open('cameras-%s.txt' % name, 'r')
         for line in f.readlines():
             pos,hpr,fov = self.unpackFixture(line)
             self.addFixture([pos[0],pos[1],pos[2],
diff --git a/direct/src/distributed/DistributedCartesianGridAI.py b/direct/src/distributed/DistributedCartesianGridAI.py
index 2ad2983aa1..370906cccc 100755
--- a/direct/src/distributed/DistributedCartesianGridAI.py
+++ b/direct/src/distributed/DistributedCartesianGridAI.py
@@ -97,7 +97,7 @@ class DistributedCartesianGridAI(DistributedNodeAI, CartesianGridBase):
     def updateGridTask(self, task=None):
         # Run through all grid objects and update their parents if needed
         missingObjs = []
-        for avId in self.gridObjects.keys():
+        for avId in list(self.gridObjects.keys()):
             av = self.gridObjects[avId]
             # handle a missing object after it is already gone?
             if (av.isEmpty()):
diff --git a/direct/src/distributed/DistributedNodeUD.py b/direct/src/distributed/DistributedNodeUD.py
index 39c0489f5e..2c83b21c07 100755
--- a/direct/src/distributed/DistributedNodeUD.py
+++ b/direct/src/distributed/DistributedNodeUD.py
@@ -26,7 +26,7 @@ class DistributedNodeUD(DistributedObjectUD):
 
     def setParentStr(self, parentToken):
         self.notify.debugCall()
-        if len(parentTokenStr) > 0:
+        if len(parentToken) > 0:
             self.do_setParent(parentToken)
 
     def setParent(self, parentToken):
diff --git a/direct/src/distributed/DoCollectionManager.py b/direct/src/distributed/DoCollectionManager.py
index 9dbf794dce..f36aedb6d9 100755
--- a/direct/src/distributed/DoCollectionManager.py
+++ b/direct/src/distributed/DoCollectionManager.py
@@ -270,9 +270,7 @@ class DoCollectionManager:
 
     def deleteDistributedObjects(self):
         # Get rid of all the distributed objects
-        for doId in self.doId2do.keys():
-            # Look up the object
-            do = self.doId2do[doId]
+        for doId, do in list(self.doId2do.items()):
             self.deleteDistObject(do)
 
         # Get rid of everything that manages distributed objects
diff --git a/direct/src/particles/ForceGroup.py b/direct/src/particles/ForceGroup.py
index b1991ad8ae..9cd37953f0 100644
--- a/direct/src/particles/ForceGroup.py
+++ b/direct/src/particles/ForceGroup.py
@@ -125,7 +125,7 @@ class ForceGroup(DirectObject):
             elif isinstance(f, AngularForce):
                 if isinstance(f, AngularVectorForce):
                     vec = f.getQuat()
-                    file.write(fname + ' = AngularVectorForce(Quat(%.4f, %.4f, %.4f))\n' % (vec[0], vec[1], vec[2], vec[3]))
+                    file.write(fname + ' = AngularVectorForce(Quat(%.4f, %.4f, %.4f, %.4f))\n' % (vec[0], vec[1], vec[2], vec[3]))
             file.write(fname + '.setActive(%d)\n' % f.getActive())
             file.write(targ + '.addForce(%s)\n' % fname)
 
diff --git a/direct/src/particles/GlobalForceGroup.py b/direct/src/particles/GlobalForceGroup.py
index c3ba10b98c..afeecb4898 100644
--- a/direct/src/particles/GlobalForceGroup.py
+++ b/direct/src/particles/GlobalForceGroup.py
@@ -1,4 +1,6 @@
 from . import ForceGroup
+from direct.showbase.PhysicsManagerGlobal import physicsMgr
+
 
 class GlobalForceGroup(ForceGroup.ForceGroup):
 
@@ -6,7 +8,7 @@ class GlobalForceGroup(ForceGroup.ForceGroup):
         ForceGroup.ForceGroup.__init__(self, name)
 
     def addForce(self, force):
-        ForceGroup.ForceGroup.addForce(force)
+        ForceGroup.ForceGroup.addForce(self, force)
         if (force.isLinear() == 0):
             # Physics manager will need an angular integrator
             base.addAngularIntegrator()
@@ -16,7 +18,7 @@ class GlobalForceGroup(ForceGroup.ForceGroup):
             physicsMgr.addAngularForce(force)
 
     def removeForce(self, force):
-        ForceGroup.ForceGroup.removeForce(force)
+        ForceGroup.ForceGroup.removeForce(self, force)
         if (force.isLinear() == 1):
             physicsMgr.removeLinearForce(force)
         else:
diff --git a/direct/src/stdpy/pickle.py b/direct/src/stdpy/pickle.py
index 77390d6853..9e7561ebb3 100644
--- a/direct/src/stdpy/pickle.py
+++ b/direct/src/stdpy/pickle.py
@@ -30,6 +30,7 @@ from copyreg import dispatch_table
 # with the local pickle.py.
 pickle = __import__('pickle')
 
+PicklingError = pickle.PicklingError
 BasePickler = pickle._Pickler
 BaseUnpickler = pickle._Unpickler
 
diff --git a/direct/src/stdpy/threading.py b/direct/src/stdpy/threading.py
index 911f35daeb..3b83e7c691 100644
--- a/direct/src/stdpy/threading.py
+++ b/direct/src/stdpy/threading.py
@@ -34,6 +34,7 @@ __all__ = [
     'Semaphore', 'BoundedSemaphore',
     'Event',
     'Timer',
+    'ThreadError',
     'local',
     'current_thread',
     'main_thread',
@@ -46,6 +47,7 @@ TIMEOUT_MAX = _thread.TIMEOUT_MAX
 
 local = _thread._local
 _newname = _thread._newname
+ThreadError = _thread.error
 
 class ThreadBase:
     """ A base class for both Thread and ExternalThread in this
diff --git a/tests/physics/test_GlobalForceGroup.py b/tests/physics/test_GlobalForceGroup.py
new file mode 100644
index 0000000000..2f0f2e23f4
--- /dev/null
+++ b/tests/physics/test_GlobalForceGroup.py
@@ -0,0 +1,19 @@
+from direct.particles.GlobalForceGroup import GlobalForceGroup
+from panda3d import physics
+
+
+def test_GlobalForceGroup():
+    gfg = GlobalForceGroup()
+
+    force1 = physics.LinearVectorForce((1, 0, 0))
+    force2 = physics.LinearVectorForce((0, 1, 0))
+    gfg.addForce(force1)
+    assert tuple(gfg) == (force1,)
+    gfg.addForce(force2)
+    assert tuple(gfg) == (force1, force2)
+    gfg.removeForce(force1)
+    assert tuple(gfg) == (force2,)
+    gfg.removeForce(force1)
+    assert tuple(gfg) == (force2,)
+    gfg.removeForce(force2)
+    assert tuple(gfg) == ()
diff --git a/tests/stdpy/test_pickle.py b/tests/stdpy/test_pickle.py
index 303c5559c1..3e8a7dcd25 100644
--- a/tests/stdpy/test_pickle.py
+++ b/tests/stdpy/test_pickle.py
@@ -1,4 +1,5 @@
-from direct.stdpy.pickle import dumps, loads
+from direct.stdpy.pickle import dumps, loads, PicklingError
+import pytest
 
 
 def test_reduce_persist():
@@ -9,3 +10,12 @@ def test_reduce_persist():
 
     parent2, child2 = loads(dumps([parent, child]))
     assert tuple(parent2.children) == (child2,)
+
+
+def test_pickle_error():
+    class ErroneousPickleable(object):
+        def __reduce__(self):
+            return 12345
+
+    with pytest.raises(PicklingError):
+        dumps(ErroneousPickleable())
diff --git a/tests/stdpy/test_threading.py b/tests/stdpy/test_threading.py
new file mode 100644
index 0000000000..557a9e428e
--- /dev/null
+++ b/tests/stdpy/test_threading.py
@@ -0,0 +1,7 @@
+from direct.stdpy import threading
+import pytest
+
+
+def test_threading_error():
+    with pytest.raises(threading.ThreadError):
+        threading.stack_size()